Miyagi1007

Hello guys so i bought a used alienware m17x r3 with hd 6870m on it, so when i was trying to boot well it goes to the windows 7 loading screen that says starting windows after that the screen turns white and goes to bsod saying atikmpag.sys also i attempt to switch my integrated gpu to my discrete card ( hd6870m) and i wont switch at all Responses are highly appreciated Thank you in advance